Telegraph receiving system



Feb. V10, 1931. F. J. SINGER 1,791,577

TELEGRAPH RECEIVING SYSTEM Filed March 20, 1929 filial I INVENTOB Z'Jkzyzr war 2;

ATTORN EY Patented Feb. 10, 1931 UNITED STATES PATENT OFFICE FRED J. SINGER, 0F ROOKVIBLE (CENTER, NEW YORK, ASSIGNOR T0 AMERICAN TELE- PHONE AND TELEGRAPH .GOMPANY, A GORPORATIONOF NEW YORK TELEGRAPH RECEIVING SYSTEM Applieatipn filed March 20, 1929. Serial No. 348,498.

This invention relates to electromagnetic relays which may be employed in signaling systems, and particularly to arrangements for operating a direct current relay from the contacts of an alternating current relay.

The relay arrangement to be described hereinafter may be, employed for receiving alternating current pulses such as are characteristic of carrier telegraphy. This relay arrangement is particularly adaptable for receiving alternating currents of especially low frequency. Pulses of alternating current are converted into pulses of direct current, each pulse of direct current corresponding to each received pulse of alternating current.

One of the objects of-this invention is to provide an improved arrangement for receiving signals such as are characteristic of carrier telegraphy.

Another of the objects of this invention is to provide an arrangement for receiving alternating current pulses and to convert these pulses into corresponding direct current pulses with small or negligible distortion, in which the lengths of the direct current pulses correspond very closely to the lengths of the direct current pulses at the sending end. I.

Another of the objects of this invention is to provide an arrangement for interconnecting an alternating current relay, or any relay the armature of which may vibrate at a frequency between the limits of a predetermined band, or at a multiple of that fre- I quency, and'a direct current relay, so that the direct current relay may be continuously operated throughout the period during which suitable alternating current of the proper frequency is applied to the winding of the alternating current relay.

While this invention will be pointed out with particularity in the appended claims, the invention itself both as to its further objects and features will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing, in which Figure 1 represents an embodiment of the invention,

and Fig. 2 represents both halves of an alternating current cycle disclosing the points at which the apparatus of Fig. 1 is particularly responsive.

Referring to Fig. 1 of the drawing, a line L is shown over which pulses of alternating or carrier current are transmitted in accordance with marking and spacing signals. The current transmitted over line L may have a definite frequency or it may be composed of a plurality of frequencies constituting a band on either side of some definite carrier. A band filter F receives this current, freely transmitting such component frequencies as lie between its predetermined limits and substantially suppressing all other frequencies. While this band filter may be of any well known type, it is preferably of the-type disclosed in the patent to G. A. Campbell, No. 1,227,113, dated May 22, 1917.

The output of the filter is impressed upon the winding of a broadly tuned alternating current relay through apotentiometer P, the potentiometer being employed for controlling the magnitude of the voltage of the impressed current. This alternating current relay is designated by the reference character R and it includes a rather stiff armature which may vibrate between contacts 1 and 2 on either side thereof. When no current is impressed upon the winding of relay R the armature is in its mid-positlon and does not close either of the specified contacts. These contacts are connected to resistances Z and Z and the point common to these resistances is grounded.

It will be apparent that when alternating current of the proper frequency is impressed upon relay R current will be transmitted by the band filter F and will energize the winding of relay R causing its armature to vibrate between contacts 1 and 2 approximately at the frequency of the impressed carrier current. It will also be apparent that the .band filter F does not form an indispensable element in the circuit arrangement shown, and that it may be omitted especially if the relay R is one selectively responsive to currents ofthe proper frequencies, the armature of this relay closing both of the associated contacts only when such currents are impressed. V.

A direct current relay havin three windings is designated by the re erence" character 11 The armature of this relay may vibrate between contacts 3 and 4 on either side thereof, contact 3 being closed in accordance with a marking signal and contact 41in accordance with a spacing signal. In order to render the following descri tion readily understandable, the three win ings of this relay will be designated W W and e 'W respectively.

A line which is suitable for transmitting direct current pulses characteristic of telegraphy is designated L This line is direct y connect-ed to the axis of rotation of the armature of relay R The contacts 3 and 4 betweenwhich the armature of relay R may vibrate are serially connected with resistances Z and Z and batteries B and B respectively the point common to these batteries being grounded. When the armature of relay R closes contact 3, current derived from battery B flows over line L through resistance Z yet when this armature closes contact 4, current of battery B flows over line L through resistance Z A battery B supplies the currentnecessary to energize the windings W and W of relay R The first of these windings W is always connected in a local circuit with battery B through a resistance Z the resistance controlling the magnitude of the continuous current The second winding of relay R designated W is connected to battery ]3 through a resistance Z and currentrflows from battery B, through winding W whenever the armature of relay R closes either of the contacts 1 or 2. 7

A so-called kickv transformer designated T is placed between the alternating current relay R and the direct current relay R The primary winding of this transformer is con-' nected between the airis or rotation of the armature of relay Bi and winding W of relay R' The secondary winding of this transformer is connected in' a local circuit in series with Winding W of relay B A condenser C is connected between the conductor attached to the axis of armature R and ground, and this condenser is preferably one having a sufficiently large capacity so as to require a period of time equal to a few cycles of the alternating current impressed on relay R3 to become charged completely to the voltage of battery B i When no alternating current flows over line L the winding of relay R will not be energized and its armature will remain in the center or mid-position. Current will continuously flow from 'battery B through the winding W of relay R causing the armature of this relay to be biased against contact 4. Current will flow through winding W of relay R of an amount sufiicient only to cause condenser C to remain charged to the voltage of battery B but this current through winding W will be insuflicient to overcome the biasing effect of winding W on the armature of the direct current relay.

When a pulse of alternating current of proper frequency is received the armature of relay R will vibrate between contacts 1 and 2 at the frequency of the impressed current and certain changes will be brought about in the condition of the circuit particularly so far as it relates to the charge of condenser C and to the flow of current through winding W to cause a corresponding movement of the armature of the direct current relay. The positive and negative halves of a complete alternating current cycle are shown in Fig. 2, and the effects upon the apparatus shown in Fig. 1 in response to received current will now be considered in more detail in connection with Fig. 2.

With the impression of current or the proper frequency upon line L, and therefore upon the winding of relay R the armature of relay R may close contact 1 at some such point in the positive half of the cycle as is designated (1. Accordingly, there will be a substantial flow of current through the winding W of relay R the circuit which is closed and effecting the flow of current including battery B resistance Z winding XV the primary winding of transformer T, the ar mature of relay R contact 1, resistance Z, and ground. The resistance interposed in the circuit just traced may be such as to cause a flow of current through winding \V which is considerably greater than the flow of current continuously established through winding W In fact, the current flowing through winding W may be practically twice as great as that flowing through winding 1V Sine-o winding l/V is wound in a direction opposite to that in which winding W is wound, the electromagnetic effect of winding XV: will be greater than that produced by winding W and, accordingly, the armature of relay R will leave contact 4 and soon close contact 3. Durin the closure of contact 1 by the armature 0F somewhat to a lower voltage.

As a point such as b is reached in the alter-- B Due to the flow of current into the condenser C, the electromagnetic c'll'cci' produced by winding W will continue to be less than that produced by winding XV: throughout the entire length of time required 1" or the armature of relay R to'travel from conrelayR condenser C discharges ing W will be considerably greater than that of winding W and therefore, the armature of relay R will remain closed against contact 3. As in the case when the armature of relay R was on contact 1, during the closure of contact 2 condenser C will again become partly discharged.

Further on in the alternating current cycle and at a point close to that designated 03, the

armature of relay R will open contact 2 and begin traveling toward contact 1. While the armature is in motion a current will continue to flow from battery B through winding W and willtend to more fully charge condenser C. During the entire interval of time required by the armature of relay R to travel from contact 2 to contact 1, the net electromagnetic etfect of winding W will be greater than that of winding W and therefore the armature of relay R will remain closed against contact 3 throughout this entire interval. J

From the consideration of the complete cycle shown in Fig. 2, it will be apparent that a current of more than an infinitesimal amplitude will be required to cause the armature of relay R to close contact 1. This is due primarily to the relative stiffness of the armature, a substantial magnetic effect being required to swing it entirely to contact 1. It will be apparent that as the relative stiffness of this armature is increased, the greater will be the amplitude of the current required to cause the closure of contact 1, and vice versa. It will also be apparent that the armature begins to leave contact 1 somewhat before the current amplitude reaches the zero value. This is also due to the relative stiffness of the armature.

The condenser C is a necessary element in the arrangement disclosed. Were it not present, a pulse of alternating current, though causing the same motion of the armature of relay R as already described hereinabove, would cause a pulsating current having large changes in amplitude to fiow through Winding W the current through Winding W first being at a zero value, rising to a maximum and then descending to the zero value, etc. This might cause the armature of relay R to Vibrate somewhat in synchronism with the armature of relay R Thus, the presence of condenser C smooths out the current flow through winding W When the armature of relay R vibrates in response to a pulse of-alternating current of the proper frequency, the condenser C will prevent the current flowing through winding W from ever reaching a zero value. In fact, condenser C is preferably one having a sufficiently large capacity, thereby permitting a substantial current to flow through winding W; when the armature of relay R is in motion, so that the current through winding W2 may produce a magnetic effect greater than that of. winding W The value of the capacity of condenser Cybowever, must not be too large, for it may then prevent the armature of relay R from leaving contact 3 for a longer period than is desirable after the alternating current has ceased to flow through a the windings of relay R at the end of the signal pulse.

The winding W of relay R is one employed to bias the armature against contact t when the armature of relay R does not vibrate between contacts-l and 2. It will be the other (not shown), or by any other means.

It is to be noted that the transformer T,

has a primary winding interposed serially or by positioning thearmature nearer one pole of the relay than between the axis ofrotation of the armature of relay R and-winding W of relay R Since the secondary winding of transformer T is serially connected to winding W3 of relay R this transformer tends to further couple windings W and W of relay R When a small increasing current flows through winding W the transformer will act to build up a substantial magnetic efi'ect about winding W}, and therefore the relay R will act more promptly and more positively. On the other hand, when the armature of relay R ceases to vibrate between contacts 1 and 2, transformer T will tend to set up a current in its secondary which will cause winding VV to assist winding W in retracting the armature. In eflect, then, the transformer tends to cause the direct current relay to become accurately responsive to the envelope of the signals transmitted in the form of alternating current pulses. 7 While this invention has been described in a certain particular arrangement merely for the sake of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. The combination of an alternating current relay tuned so that itsarmature may vithe frequency of the impressed current varies between predetermined limits, a direct current relay having a pair of windings, a source of direct current potential, one of the windings of said direct current relay being connected to said source of potential so as to bias the armature of the direct current relay in one direction, and a condenser of large capacity, the other winding of said direct current relay being connected to said source of potential through the armature of the alternating current relay when it closes either of its contacts and accordingly biases the armature of the direct current rela in the opposite direction, the condenser being connected across the armature of the alternating current relay and its contacts and maintaining the flow of current through the latter winding of the direct current relay practically constant. p

2. The combination of an alternating current relay the armature of which moves be tween two contacts which are connected in a localcircuit, a direct current relay, a source of directcurrent potential, a condenser of large capacity connected between the armature of the alternating current relay and the local circuit connecting its contacts, said condenser, the winding of the direct current relay, and the source of direct current potential being connected in a series circuit.

3. The combination of an alternating current relay having two contacts between which its armature may vibrate, two resistances connected serially with said contacts, a source of 7 potential, a direct current relay, and a condenser of large capacity, said condenser being connected between the armature of the alternating current relay and a point common to said resistances, the condenser being connected in series with said source of direct current potential through the winding. of the direct current relay.

l. The combination of an electromagnetic relay operatively responsive only to alternating currents within a narrow band of frequencies on each side of some predetermined frequency, a direct current relay having a pair of windings, a source of direct current, means whereby one of the windings of the direct current relay may .be energized with current from said source when the electromagnetic relay responsive to alternating currents is energized, and means to continuously energize the otherof the windings of the direct current relay even during intervals when the electromagnetic relay responsive to alternating currents is not energized.

5. The combination of a band filter freely transmitting currents of a narrow band of frequencies on each side of a definite frequency, an alternating current relay of the electromagnetic type of operatively responsive only to the currents transmitted by said band filter, a direct current relay having two windings, a source of direct current potential,

one of the windings of the direct current relay being-continuously energized by the flow of current from said source of direct current potential, and means to energize the other of the windings of said direct current relayto operate said-direct current relay continuously throughout the interval of time during which said alternating current relay is operated in response to current transmitted by the band filter.

6. The combination of an alternating current relay having an armature free to move between two contacts, a direct current relay, a battery, the winding of the direct current relay, the armature of the alternating current relay and. the battery being connected in a series circuit, and a condenser shunting that part of the series circuit including the wind mg of the direct current relay and the battery, said condenser becoming charged to the voltage of the battery when the armature of the alternating current relay does not close either of its associated contacts and becoming discharged to a certain degree when the armature of the alternating current relay does close either of its associated contacts.

7 The combination of a band filter freely transmitting currents of frequencies between a pair of definite limits, an alternating cur rent relay responsive to the currents transmitted by said band filter, two resistances connected in series between the contacts between which the armature of the alternating current relay may vibrate, a direct current relay having two windings, a source of direct current potential, and a condenser, one winding of the direct current relay and the source of direct current potential being connected in a series circuit, the other winding of the direct current relay, the source of direct current potential, the armature of the alternating current relay, and the resistances connected to the contacts between which said armature vibrates being also connected in a series circuit, said condenser shunting the circuit including the armature of the alternating current relay and the resistances connected to its contacts.

8. The'combination of a direct current relay, an alternating current relay of the electromagnetic type, a condenser, a circuit illcluding said condenser coupling said alternating current relay to the direct current relay to continuously operate the latter relay when alternating current is impressed upon the winding of the former relay, and means coupled to said circuit to accelerate the responsive action of the direct current-relay when alternating current is intermittently impressed upon the winding of said alternating current relay.

9. In a system for receiving pulses of alter nating current representing marking and spacing signals characteristic of telegraphy, the combination of an alternating current relay or electromagnetic structure, a direct current relay, a condenser, a circuit arrangement including said condenser coupling said relays and transmitting a substantial current through the winding of the direct current relay when current is applied to the winding of the alternating current relay, and means for coupling said circuit arrangement with said direct current relay to accelerate the w responsive action of the direct current relay as current is intermittently applied to the alternating current relay in accordance with marking and spacing signals.

10. In a telegraph receiving system, the

combination of an alternating current relay of electromagnetic structure, a direct current relay having three coupled windings, a source of direct current potential, the first of the direct current relay windings being continuously energized with current from said source, means whereby the second of said windings may be energized with current from said source during intervals when said alternating current relay is responsive to a received pulse,

and a transformer for coupling the second and third windings of said direct current relay to accelerate the action of the armature of the latter relay when pulses of current are intermittently applied to said alternatin current relay in accordance with marking and spacing signals.

In testimony whereof, I have signed my name to this specification this 18th day or" March, 1929.

FRED J. SINGER. 

